Physical Exertion Is Key to Keeping Weight Off

Persistent increased physical activity is likely essential for long-term maintenance of weight loss, new research from participants in the US TV reality show The Biggest Loser suggests.

The new data were presented October 31, 2017 here at Obesity Week 2017 and published in Obesity by Jennifer C Kerns, MD, of the Washington, DC Veterans Affairs Medical Center, and colleagues.

Using objective measures for both energy intake and physical activity in 14 former Biggest Loser contestants 6 years after they participated in the competition, Dr Kerns and colleagues found that those who had regained the least weight were the most active, and vice versa.

Food intake, on the other hand, had very little effect on long-term weight-loss maintenance.

"The Biggest Loser participants who were the most successful in maintaining lost weight had the greatest increase in physical activity after 6 years. Our results support previous recommendations that large, persistent increases in physical activity may be required for the long-term maintenance of lost weight," say Dr Kerns and coauthors.

Asked to comment, Eric Ravussin, PhD, Boyd Professor at Louisiana State University, Baton Rouge, and coeditor of Obesity, told Medscape Medical News that the data align with those of follow-ups to major trials — including the Diabetes Prevention Program and the Action for Health Diabetes (Look AHEAD) study as well as with the National Weight Control Registry — of thousands of people who have lost at least 30 pounds and kept them off for at least a year.

"The successful losers ... all report high levels of physical activity" for weight maintenance, in contrast to weight loss, for which caloric deficit plays a far greater role, Dr Ravussin noted.

"I think we have to distinguish the weight-loss phase vs the weight-loss maintenance. For the weight-loss phase, the best way is really calorie restriction," he said, but added that it's best to begin engaging in exercise at that time too, in order to become accustomed to it for the later maintenance phase.

The reason for the difference between what works for weight loss vs maintenance, he said, probably has a lot to do with metabolic adaptation.

This was the subject of another Biggest Loser paper published in Obesity in 2016, in which a person's metabolism slows down in response to a large drop in weight, making weight-loss maintenance difficult without an extra "push" from exercise, he explained.

35 Minutes of Intense Exercise/Day to Maintain Weight Loss

The subjects in the new study were 14 participants with class III obesity who participated in a single season of The Biggest Loser, during which they underwent an intensive 30-week diet and exercise program and lost an average of 60 kg. Most regained weight after the program ended, although the degree of regain was highly variable.

The median weight loss after 6 years was 13%. Seven subjects above the median weighed 24.9% less than baseline (maintainers) while the seven below the line (regainers) weighed 1.1% above their baseline (P = .0005).

At baseline, 6 weeks, 30 weeks, and 6 years after the competition, the subjects' body composition was measured via dual energy X-ray absorptiometry (DEXA), resting energy expenditure was measured by using indirect calorimetry, and energy intake and physical activity were assessed using doubly labeled water, a method of measuring energy consumption based on the estimation of the rate of carbon-dioxide elimination from the body.

At 6 years, mean physical activity was 12.2 vs 8.0 kcal/kg/day for the maintainers and regainers, respectively, also significantly different (P = .04).

Dr Ravussin noted that one of the study's limitations is that the objective measures used to assess physical activity couldn't ascertain anything about the type, intensity, or duration of the exercise, but he said that 35 minutes a day of intensive exercise, or 60 minutes of moderate activity, would roughly approximate the calorie expenditures among the maintainers.

On the other hand, energy intake from baseline didn't differ at 6 years (-8.7% for maintainers vs -7.4% for regainers, respectively (P = .83).

For all 14 participants, there was no significant correlation between absolute or percent weight loss at the end of the competition with those values 6 years later.

The percent of weight change after 6 years was not significantly correlated with percent change in energy intake from baseline (P = .36), but it was significantly correlated with percent change in physical activity (P = .017).

Dr Ravussin concluded: "It's small sample size and it's a special group, but I think it's a very nice study showing that physical activity works for weight-loss maintenance."

Dr Kerns was previously a contestant on another season of The Biggest Loser as well as a medical consultant. Dr Ravussin was a coauthor on the original Biggest Loser study but hasn't been involved in the enterprise for several years and was not involved in the current study.